diff --git a/src/store/dto/store-items.dto.ts b/src/store/dto/store-items.dto.ts
index ec29397..bc9cb2e 100644
--- a/src/store/dto/store-items.dto.ts
+++ b/src/store/dto/store-items.dto.ts
@@ -8,6 +8,7 @@ import {
   IsString,
   Min,
   MinLength,
+  ValidateIf,
   ValidateNested,
 } from 'class-validator';
 
@@ -21,21 +22,34 @@ export class StoreItemVariantSelectionDto {
   optionId!: string;
 }
 
+/** Keep null as null; avoid `Number(null) === 0`. */
+function nullableNumber({ value }: { value: unknown }) {
+  if (value === null || value === undefined || value === '') return null;
+  const n = typeof value === 'number' ? value : Number(value);
+  return Number.isFinite(n) ? n : value;
+}
+
 export class CreateStoreItemVariantDto {
   @IsArray()
   @ValidateNested({ each: true })
   @Type(() => StoreItemVariantSelectionDto)
   selections!: StoreItemVariantSelectionDto[];
 
+  /** null / omitted = contact for price */
   @IsOptional()
+  @Transform(nullableNumber)
+  @ValidateIf((_, v) => v !== null && v !== undefined)
   @IsNumber()
   @Min(0)
-  price?: number;
+  price?: number | null;
 
+  /** null / omitted = unlimited stock */
   @IsOptional()
+  @Transform(nullableNumber)
+  @ValidateIf((_, v) => v !== null && v !== undefined)
   @IsInt()
   @Min(0)
-  stockQuantity?: number;
+  stockQuantity?: number | null;
 }
 
 export class BatchCreateStoreItemsDto {
@@ -117,14 +131,18 @@ export class ListPublicStoreItemsDto {
 
 export class UpdateStoreItemVariantDto {
   @IsOptional()
+  @Transform(nullableNumber)
+  @ValidateIf((_, v) => v !== null && v !== undefined)
   @IsNumber()
   @Min(0)
-  price?: number;
+  price?: number | null;
 
   @IsOptional()
+  @Transform(nullableNumber)
+  @ValidateIf((_, v) => v !== null && v !== undefined)
   @IsInt()
   @Min(0)
-  stockQuantity?: number;
+  stockQuantity?: number | null;
 
   @IsOptional()
   @IsNumber()
@@ -167,13 +185,19 @@ export class SyncStoreItemVariantRowDto {
   @Type(() => StoreItemVariantSelectionDto)
   selections!: StoreItemVariantSelectionDto[];
 
+  /** null = contact for price */
+  @Transform(nullableNumber)
+  @ValidateIf((_, v) => v !== null && v !== undefined)
   @IsNumber()
   @Min(0)
-  price!: number;
+  price!: number | null;
 
+  /** null = unlimited stock */
+  @Transform(nullableNumber)
+  @ValidateIf((_, v) => v !== null && v !== undefined)
   @IsInt()
   @Min(0)
-  stockQuantity!: number;
+  stockQuantity!: number | null;
 }
 
 export class SyncProductStoreItemVariantsDto {
diff --git a/src/store/store-items.service.ts b/src/store/store-items.service.ts
index b0e5da3..de3d004 100644
--- a/src/store/store-items.service.ts
+++ b/src/store/store-items.service.ts
@@ -916,11 +916,11 @@ export class StoreItemsService {
     existingKeys.add(key);
     batchKeys.add(key);
 
-    if (item.price !== undefined && item.price < 0) {
+    if (item.price != null && item.price < 0) {
       throw new BadRequestException('Price cannot be negative');
     }
 
-    if (item.stockQuantity !== undefined && item.stockQuantity < 0) {
+    if (item.stockQuantity != null && item.stockQuantity < 0) {
       throw new BadRequestException('Stock cannot be negative');
     }
   }